Type “cancer risk assessment” into Google, and you’ll come up with a list of assessment tools for particular cancers, most with a strong focus on personal risk factors related to lifestyle, exposures, and medical and family history. Would it help also to get a broader view of cancer risk? The National Cancer Institute thinks so. NCI has teamed with Dartmouth researchers Steven Woloshin, MD, and Lisa Schwartz, MD, to create “Know Your Chances,” a website that aims to put cancer risk in perspective.
“We want to get people to understand the risks of dying from specific cancers in comparison to each other and to noncancer causes of death, and at different times in their lives,” said Eric J. (Rocky) Feuer, PhD, chief of the Statistical Research and Applications Branch in NCI’s Surveillance Research Program and the senior investigator in this project. Without this larger picture, it’s hard to make sense of cancer statistics, according to Woloshin and Schwartz, both professors at the Dartmouth Institute for Health Policy and Clinical Practice and codirectors of its Medicine in the Media Program.
“It’s difficult to read a newspaper or magazine, watch television, or surf the Internet without hearing about cancer,” they say in the introduction to the website. “Unfortunately, these messages are often missing basic facts needed for people to understand their chance of cancer: the magnitude of the chance and how it compares with the chance of other diseases.”
The Charts
“Know Your Chances” has four sections:
- Big-picture charts give the chance of dying over ten-year periods, by age, sex, and race for different cancers; other major causes of death; and all causes combined.
- Custom charts allow users to generate charts by age, sex, and race for different causes of death and over different time frames.
- Your chances let users see leading causes of death by sex, race, and exact age.
- Special cancer tables show the risk of diagnosis, as well as death, for particular cancers and across cancer sites.
The data and estimates for the new charts come from NCI’s DevCan statistical algorithms and database. DevCan calculates probabilities of developing and dying from specific cancers by using incidence data from the agency’s Surveillance, Epidemiology, and End Results (SEER) program; mortality counts from the National Center for Health Statistics; and US census data.
The idea of comparing probabilities and using other ways to provide a broader context builds on earlier work by the Dartmouth researchers, who have published widely on the communication of medical and statistical information, especially in relation to risk.
“We saw an opportunity to marry the kind of calculation we do to the kind of risk communication messages they do,” said NCI’s Feuer.
Accurate risk communication messages are based on several principles, Schwartz and Woloshin said. One is to put the number of deaths in numerical context—e.g., three of 100 people, or 3%—rather than the absolute number of people expected to die of a disease. Give the denominator, in other words, as well as the numerator. Another is to avoid making statements of relative risk without giving actual figures. A 50% risk reduction sounds large but may not mean much if risk is reduced from 4% to 2%. But if risk is reduced from 60% to 30%, a 50% reduction can mean a lot.
A guiding principle is to put risks in accurate perspective. “We wanted to put risk in context,” Schwartz said, “by using denominators, by comparing each specific cancer to other cancers and other major causes of death, and by using standardized time frames and formats.”
The ten-year time frame is arbitrary but makes sense, they said, because it avoids the exaggerated risk that comes with time frames that are too long as well as those that are too short. “Over-a-lifetime risk distorts the picture, but so can too short a time frame,” Woloshin said. That can cause you to underestimate your risk.”
The ten-year time frame also allows people time to do things such as make lifestyle changes or consider proven screening tests, they note on the website.
Setting Priorities
The charts present risk by age, sex, and race, but so far not by factors related to lifestyle or heredity. However, NCI plans to add smoking, the single most important risk factor for a variety of cancers and other causes of death.
In an earlier version of the charts, the Dartmouth authors included how smoking affects risk. Data and methods are now being updated using National Health Interview Surveys that include smoking status and follow-up data on mortality and cause of death. As for family history, lifestyle, and other risk factors, finding comparable data sources may be more problematic.
“We have to consider feasibility,” Schwartz said. “Right now we don’t have good data for all of them. But even with extra risk factors we might not know that much more.”
In any case, “Know Your Chances” is not designed to do exactly the same thing as other risk assessment tools, which may provide estimates for a single disease as a function of several risk factors. Instead, it could complement them, Feuer said. “We see it as providing breadth, giving the broad landscape. It could help a person make decisions about priorities—diabetes, lung cancer, heart attack, for instance—before making decisions about lifestyle changes or screening.
“Both facts and values go into decision making,” Woloshin noted. “These charts give facts. The values are individual, how you process the facts. Research has shown people process the same facts differently.”
That finding suggests that the charts’ facts could be the basis for doctor–patient discussions of risks and what to do about them.
In fact, “the charts could be the first step in a huge educational process,” said Otis Brawley, MD, chief medical officer of the American Cancer Society. He said physicians could use the charts to help patients avoid the common pitfall of exaggerating the chance of dying from one disease, such as prostate cancer, while minimizing the greater chance of dying from others. For instance, a 55-year-old white man has a one in 1,000 chance of dying from prostate cancer within ten years, compared with two in 1,000 for high blood pressure, three in 1,000 for stroke, and ten in 1,000 for lung cancer, according to the charts.
“One of the great problems we deal with in our society is that people don’t understand or they misperceive risk,” Brawley said. “These charts could reduce a lot of mental anguish and a lot of concern.”
A version of this article originally appeared in the Journal of the Nation Cancer Institute.
Featured Image credit: Cancer by PDPics. CC0 Public Domain via Pixabay.
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